1. Field of the Invention
The present invention relates to a recording apparatus and a processing method executed by the recording apparatus.
2. Description of the Related Art
A conventional recording apparatus executes recording of an image on a recording medium. When data regarding an image to be recorded is received from a host apparatus, the conventional recording apparatus rasterizes the received data into binary bitmap data. In addition, the recording apparatus transfers the bitmap data to a recording head to execute the recording process.
As a method for rasterizing multivalued data into bitmap data, a conventional method generates and uses a rasterization table (i.e. a dot matrix) for the gradation (e.g. color-ranking or shade-ranking) of each pixel. In executing rasterization described above, if a fixed rasterization table (dot matrix) only is provided for the gradation of pixels and if the pixels have the same gradation, then the same rasterization pattern is obtained (i.e. a series of pixels with the same color or shade is printed). In executing rasterization using a fixed pattern, banding or image unevenness may occur due to smear on nozzles or unevenly discharged ink.
In order to address the above-described problem, a conventional method generates and uses a plurality of dot matrices for the gradation of each pixel. The conventional method like this selects one from among the plurality of matrices to execute rasterization. In this case, the pattern corresponding to each gradation is not fixed. Accordingly, the influence from the smear on the nozzles may not easily arise. Therefore, the conventional method is capable of reducing or suppressing unevenness that may otherwise occur due to unevenness of the mechanical accuracy of a recording head. In other words, a smoother transition of colour or shade from one pixel to the next in a raster is possible because the pixel colours or shades are determined based on one of several possible overall dot matrices.
Various methods for selecting one from among a plurality of dot matrixes have been conventionally proposed. Japanese Patent Application Laid-Open No. 09-046522 discusses a method for changing a dot matrix to be used for rasterization on gradation every time data having the same gradation is processed.
However, if the method discussed in Japanese Patent Application Laid-Open No. 09-046522 is used, the dot matrix is changed in order of appearance (i.e. in a printing direction) of data. Accordingly, a result of the rasterization in the forward raster direction (the forward scanning direction) may be different from a result of the rasterization in the backward raster direction (the backward scanning direction). Accordingly, in this case, it is necessary to fix the direction of rasterization.
In addition, a recording apparatus may include a plurality of recording modes, such as a single-pass recording mode and a multipass recording mode, either mode in which both single direction recording and bidirectional recording can be executed. Accordingly, in order to appropriately select a dot matrix, it is necessary also to consider the recording mode.
In the method discussed in Japanese Patent Application Laid-Open No. 09-046522, bitmap data that has been subjected to rasterization is stored on a buffer. In this case, it is necessary to secure a storage area larger than that necessary in storing multivalued data on a buffer without rasterizing it. Accordingly, the costs of manufacture may increase.
On the other hand, it is desired by the market that recording is executed at a high speed and that costs of manufacture of a recording apparatus is reduced. Therefore, it is necessary to reduce the time taken in executing rasterization processing. In addition, it is necessary to simplify the circuitry configuration of a recording apparatus.